Content-aware inter-RAT RAB steering

ABSTRACT

A method for congestion control at an eNodeB is described, comprising detecting congestion at an eNodeB and entering a congestion control mode, receiving, at the eNodeB, a new user equipment (UE) connection request that contains a radio resource control (RRC) establishment cause, and using the RRC establishment cause for identifying a congestion management strategy, the congestion management strategy comprising one of initiating a handover for an existing LTE bearer, or redirecting the new UE connection request to a 3G nodeB.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application in a continuation under 35 U.S.C. § 120 of U.S. patentapplication Ser. No. 15/076,644, filed Mar. 21, 2016, entitled“Content-Aware Inter-RAT RAB Steering” which itself is a non-provisionalconversion of, and claims the benefit of priority under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 62/135,984, filed onMar. 20, 2015 and entitled “Content-Aware Inter-RAT RAB Steering,” whichis hereby incorporated by reference in its entirety for all purposes.The present application also hereby incorporates by reference U.S. Pat.No. 8,879,416, “Heterogeneous Mesh Network and Multi-RAT Node UsedTherein,” filed May 8, 2013; U.S. Pat. No. 9,113,352, “HeterogeneousSelf-Organizing Network for Access and Backhaul,” filed Sep. 12, 2013;U.S. patent application Ser. No. 14/034,915, “Dynamic Multi-AccessWireless Network Virtualization,” filed Sep. 24, 2013; U.S. patentapplication Ser. No. 14/510,074, “Parameter Optimization and EventPrediction Based on Cell Heuristics,” filed Oct. 8, 2014; U.S. patentapplication Ser. No. 14/642,544, “Federated X2 Gateway,” filed Mar. 9,2015; U.S. patent application Ser. No. 14/828,432, “Inter-CellInterference Mitigation,” filed Aug. 17, 2015; U.S. patent applicationSer. No. 14/936,267, “Self-Calibrating and Self-Adjusting Network,”filed Nov. 9, 2015; U.S. patent application Ser. No. 15/002,383,“Multi-Rat Heterogeneous Carrier Aggregation,” filed Jan. 20, 2016; U.S.patent application Ser. No. 14/942,950, “Seamless Mobile Handover,”filed Nov. 16, 2015; and U.S. Provisional Pat. App. No. 62/310,173,“IuGW Architecture,” filed Mar. 18, 2016, each in its entirety for allpurposes, respectively.

BACKGROUND

Presently, Long Term Evolution (LTE), a 4G standard, and the UniversalMobile Telecommunications System (UMTS), a 3G standard, along with other3G and 4G standards, coexist in the marketplace and in mobile operatordeployments. It is anticipated that this coexistence will continue forsome time, including the period during which both are in active use aswell as the period during which 3G is phased out. A way to use both 3Gand 4G resources productively, such as during congestion periods, istherefore desirable.

The present disclosure describes systems and methods for performingsteering, i.e., direction and/or redirection, of a UE or a radio accessbearer (RAB) from one radio access technology (RAT) to another,including from 3G to 4G and from 4G to 3G, thereby providing congestionrelief. Specific parameters and strategies are described therefor.

SUMMARY

A method is disclosed, comprising: detecting congestion at an eNodeB andentering a congestion control mode; receiving, at the eNodeB, a new userequipment (UE) connection request that contains a radio resource control(RRC) establishment cause; using the RRC establishment cause foridentifying a congestion management strategy, the congestion managementstrategy comprising one of initiating a handover for an existing LTEbearer, or redirecting the new UE connection request to a 3G nodeB.

The method further involves wherein detecting congestion at the eNodeBis performed at the eNodeB. The method further involves whereindetecting congestion at the eNodeB is performed at a coordinatingserver. The method further involves wherein the eNodeB is a multi-radioaccess technology (multi-RAT) eNodeB with an integrated UMTS nodeB. Themethod further involves further comprising using a quality of serviceclass identifier (QCI) of the existing LTE bearer to determine whetherto evacuate the existing LTE bearer. The method further involves whereinthe congestion management strategy comprises both of initiating ahandover for an existing LTE bearer, and redirecting the new UEconnection request to a 3G nodeB. The method further involves whereinthe congestion management strategy comprises initiating a handover foran existing LTE bearer if the new UE connection request has an RRCestablishment cause of either emergency or high priority access. Themethod further involves further comprising redirecting the new UEconnection request that is a request for a packet-switched (PS) dataconnection to a 3G nodeB. The method further involves further comprisingredirecting a mobile originating data connection request to a 3G nodeB.The method further involves further comprising identifying a pluralityof LTE bearers to be handed over to 3G from lowest to highest QCI value.The method further involves further comprising exiting the congestioncontrol mode once congestion at the eNodeB is resolved. The methodfurther involves further comprising redirecting 3G connections back tothe LTE eNodeB once congestion at the eNodeB is resolved. The methodfurther involves further comprising detecting congestion by tracking oneor more of: processor load; physical resource block (PRB) usage;physical downlink control channel control channel elements (PDCCH CCEs);number of total user equipments served; and backhaul bandwidthutilization.

A system is also disclosed comprising a multi-radio access technology(multi-RAT) base station comprising: a Long Term Evolution (LTE) eNodeB;a High Speed Packet Access (HSPA) nodeB coupled to the LTE eNodeB; and amulti-RAT coordination module coupled to the LTE eNodeB and the HSPAnodeB, the multi-RAT coordination module configured to perform stepscomprising: detecting congestion at an eNodeB and entering a congestioncontrol mode; receiving, at the eNodeB, a new user equipment (UE)connection request that contains a radio resource control (RRC)establishment cause; using the RRC establishment cause for identifying acongestion management strategy, the congestion management strategycomprising one of initiating a handover for an existing LTE bearer, orredirecting the new UE connection request to a 3G nodeB.

A digital storage medium is also disclosed comprising instructions that,when executed by a base station, causes the computer to perform stepscomprising: detecting congestion at an eNodeB and entering a congestioncontrol mode; receiving, at the eNodeB, a new user equipment (UE)connection request that contains a radio resource control (RRC)establishment cause; using the RRC establishment cause for identifying acongestion management strategy, the congestion management strategycomprising one of initiating a handover for an existing LTE bearer, orredirecting the new UE connection request to a 3G nodeB.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system providing multi-RAT service,according to some embodiments.

FIG. 2 is a state diagram showing multiple states of an HSPA and an LTEprotocol stack at a HSPA base station and an LTE base station, inaccordance with some embodiments.

FIG. 3 is a flowchart showing a method for providing congestion reliefat an eNodeB, in accordance with some embodiments.

FIG. 4 is a schematic diagram of an enhanced eNodeB, in accordance withsome embodiments.

FIG. 5 is a schematic diagram of a gateway, in accordance with someembodiments.

DETAILED DESCRIPTION

The assumptions made regarding the below disclosure include: a UE thatis capable of 3G and 4G network access; 3G and 4G coverage over the samearea; and a inter-RAT RAN coordination mechanism, such as describedwithin U.S. Pat. App. Pub. US 20140126410, incorporated by referenceherein in its entirety for all purposes.

In the 3G/4G co-deployment context, the typical default UE behavior iscamping on or attaching to the 4G RAN preferentially over attaching tothe 3G RAN, which may lead to 4G RAN congestion during peak hours.During such peak hours, ideally traffic could be steered to the leastloaded RAT, leading to better performance. Here the service/contentaspect should also be taken into account (content-aware steering), sothat services that benefit most from LTE could use LTE, whileless-demanding services could use 3G (R99/HSPA/HSPA+).

This method provides congestion control based on inter-RAT steering, aswell as LTE-3G offload.

In the LTE system, a UE in idle mode establishes a Radio ResourceControl (RRC) connection for signaling or data transmission. The UEsends an RRC connection request message including an RRC connectionestablishment cause to an eNB to request to establish an RRC connection.The eNodeB uses the RRC connection establishment cause to prioritize theRRC connection request from the UE, e.g. at high load situations.Therefore, the UE has to include the correct RRC connectionestablishment cause for the eNodeB to prioritize the RRC connectionestablishment. Currently, in the LTE system, RRC connectionestablishment causes are defined as follows: emergency call, highpriority access, Mobile Terminating (MT) access, Mobile Originating (MO)signaling and MO data. The RRC establishment cause is sent as aninformation element (IE) that is part of the RRC connection request.

These RRC connection establishment causes are mainly used by the networkto differentiate the subsequent action upon receiving the RRC connectionrequest message. For example, the RRC connection establishment cause canbe used to perform call admission control, or to perform access barringcontrol to prioritize access of Non Access Stratum (NAS) connectionrequest types, which are mapped to RRC connection establishment causes.RRC connection establishment causes may be evacuate.

UEs are typically maintained in one of two modes, an idle mode and aconnected mode. This is true for UMTS/3G and also for LTE. The idle modeis lower power and does not require the base station to be connected.The connected mode requires greater resource commitment from the basestation. Base stations or UEs may request that a UE be moved from onebase station to another. Cell reselection happens from idle mode to idlemode (i.e. is an idle mode procedure) and is not covered further here.While in the connected mode, the base station may request a UE to attachto another base station; this is called handover. This may be anintra-radio access technology (intra-RAT) handover, to another basestation of the same RAT, or an inter-RAT handover, e.g., from 4G to 3G,from LTE RRC_CONNECTED to 3G RRC_CONNECTED/CELL_DCH, or vice versa.

Redirection is a third type of procedure in which the active basestation moves the UE from connected mode to idle mode (e.g. in manycases for circuit-switched fallback (CSFB), the UE is redirected fromLTE RRC_CONNECTED mode to 2G/3G idle mode). For example, in case ofCSFB, handover is not required or even supported by the network and/orthe UE, because 4G and 3G do not have a mechanism for directly handingoff active data flows, and in such case redirection is de facto the onlypossible mechanism to use. With redirection, although specific dataflows are not handed off, information such as frequencies of the targetbase station may be included along with the redirection request.

Typically, LTE eNodeBs perform CSFB because support for voiceconnections over LTE has only recently become available using Voice overLTE (VoLTE). However, it is possible to use the same type of redirectnot only just for circuit-switched calls, but for packet connections aswell; and to use this type of redirect to manage congestion, as well asto redirect UEs to other nodes with voice call capability.

Redirection can be faster than handover due to many reasons (e.g.inter-RAT measurement delay/cell detection, L3 filtering,time-to-trigger, handover preparation in the network etc.), especiallyin cases where a mobile-originated (MO) or mobile-terminated (MT) callthat requires the UE to move to RRC_CONNECTED state and perform CSFB istriggered from LTE idle mode.

One advantage of redirect over handover is that handover requests mayinclude obtaining measurement reports from UEs, such as from UEs fromneighboring cells or by the source eNodeB requesting that a UE providespecific inter-RAT measurement reports, which delays completion of thehandover. But a redirect does not require any measurement reports, sincethe redirect requires only a target frequency to be indicated, and thusthe redirect completes sooner than a handover. Redirection is supportedin Release 8 and above UEs.

Packet and circuit redirect requests may be marked differently. Forredirect requests that are made for circuit-switched fallback (CSFB),the redirect request may be marked with a flag indicating that this is aCS-protocol redirect request. For redirects for packet-switched dataconnections, the redirect request may be marked with a PS flag.

RRC connection establishment is used to make the transition from RRCIdle mode to RRC Connected mode. UE must make the transition to RRCConnected mode before transferring any application data, or completingany signaling procedures. The RRC connection establishment procedure isalways initiated by the UE but can be triggered by either the UE or thenetwork. For example, the UE triggers RRC connection establishment ifthe end-user starts an application to browse the internet, or to send anemail. Similarly, the UE triggers RRC connection establishment if the UEmoves into a new Tracking Area and has to complete the Tracking AreaUpdate signalling procedure. The network triggers the RRC connectionestablishment procedure by sending a Paging message. This could be usedto allow the delivery of an incoming SMS or notification of an incomingvoice call.

In some embodiments described herein, a method similar to CSFB may beused to cause RRC connection establishment in LTE to be redirected toestablishment of a connection to a 3G node.

LTE congestion may be caused by any of various reasons. In someembodiments, an enhanced base station may maintain one or morecongestion detection key performance indicators (KPIs):

1. RRC failure due to lack of resource, such as physical resource blocks(PRBs) being used up

2. Running out of physical downlink control channel (PDCCH) controlchannel elements (CCEs)

3. Exceeding limit on total # of UEs to be served concurrently

4. Exceeding limit on total # of UEs to be served within one transmittime interval (TTI)

5. Backhaul resource used up (i.e., out of upstream bandwidth forservicing the UE)

6. Processing resources used up or at high load

When one or more of the congestion KPIs is reached, reaches a highlevel, or exceeds a congestion threshold, the system could enter into acongestion management mode and could use the methods described herein.Congestion could be detected either at a cloud coordination server, suchas an LTE access controller, or at a base station.

Once congestion is detected (or the onset of congestion is detected),one of more of the following actions can be taken:

1. During the new RRC connection stage, the RRC establishment cause maybe taken into account. RRC establishment causes are sent by a UE duringthe connection request. The possible causes include: emergency; highpriority access; mobile terminating access; mobile originatingsignaling; and mobile originating data. This set of different causes canprovide bases to provide different actions under the congestionscenario.

2. If the causes are emergency or high priority access:

a. As long as 3G RAN still has enough capacity (not experiencingcongestion concurrently), identify the established LTE PDP contextsbased on QCI info.

It is possible to perform redirection of existing LTE bearers by usingthe bearer quality of service (QoS) class identifier (QCI) fieldassociated with the bearer. The QCI field is created at the eNodeB andis therefore readily available, even with encrypted traffic. Thefollowing table describes the QCI values that are available as definedin 3GPP TS 23.203, “Policy and Charging Control Architecture”:

TABLE 1 QCI Packet Packet Resource Delay Error QCI Type Priority BudgetLoss Example Services 1 GBR 2 100 ms 10−2 Conversational Voice(guaranteed bit rate) 2 GBR 4 150 ms 10−3 Conversational Video 3 GBR 3 50 ms 10−3 Real Time Gaming 4 GBR 5 300 ms 10−6 Non-ConversationalVideo (Buffered Streaming) 65 GBR 0.7  75 ms 10−2 Mission Critical userplane Push To Talk voice (e.g., MCPTT) 66 GBR 2 100 ms 10−2Non-Mission-Critical user plane Push To Talk voice 5 non-GBR 1 100 ms10−6 IMS Signalling 6 non-GBR 6 300 ms 10−6 Video (Buffered Streaming)TCP- Based (for example, www, email, chat, ftp, p2p and the like) 7non-GBR 7 100 ms 10−3 Voice, Video (Live Streaming), Interactive Gaming8 non-GBR 8 300 ms 10−6 Video (Buffered Streaming) TCP- Based (forexample, www, email, chat, ftp, p2p and the like) 9 non-GBR 9 300 ms10−6 Video (Buffered Streaming) TCP- Based (for example, www, email,chat, ftp, p2p and the like). Typically used as default bearer 69non-GBR 0.5  60 ms 10−6 Mission Critical delay sensitive signalling(e.g., MC-PTT signalling) 70 non-GBR 5.5 200 ms 10−6 Mission CriticalData (e.g. example services are the same as QCI 6/8/9)

As described herein, bearers are tagged with QCI based on the type oftraffic that is understood to be transmitted over that bearer. QCI istypically used to discard low-priority traffic according to priority,from lowest priority to highest priority. In some embodiments, QCI maybe used to identify bearers, and then to cause the bearers to beredirected or handed over to other cells, such as a 3G cell.

b. Deflecting some E-RABs into the 3G via inter-RAT handover (rankedbased on QCI preferences)

In some cases, capacity for new calls may require that existing bearersbe dropped. When a 3G packet nodeB is available, redirection of bearersto the 3G nodeB is a good solution. Bearers may be redirected, causingthem to return to IDLE mode, but since packet traffic is oftennon-interactive (i.e., not a real-time voice or video call), nointerruption is necessarily required of the user, and the inconvenienceto the user may thus be kept to a minimum.

i. QCI=1 is deflected 1st (ideally towards R99)

ii. QCI=9 is deflected to 3G best-effort

c. Proceed to the RRC connection for the current connections

3. If the causes are Mobile Originating Calls, identified via the RRCestablishment cause and a domain indicator flag set to CS, it may bepossible to try an optimized CSFB approach: reject the current RRCconnection request and redirect it to the 3G domain. Note that thisscheme can be exercised during the non-congestion state as well.

4. Otherwise, for example in the cases of MO signaling or MO data,redirect packet-switched inbound RRC connections to the 3G RAT byissuing RRC connection release with the specified 3G cell's frequencyinfo, etc. By redirecting these connections, the LTE eNodeB that iscongested will be able to continue handling its current load of bearerswithout becoming increasingly congested.

5. In some embodiments, it is possible to cause packet-switched LTEbearers that are already on the eNodeB to be reselected to a 3G RAT,just as described in step 4, but for currently-active bearers and notjust for new inbound RRC requestors.

Note that this process is reversible. Once the LTE congestion status iscleared, a set of 3G connections can be shifted back to LTE (viainter-RAT handover). Given that 3G often offers superior characteristicsfor voice calls, QCI=1 bearers would stay in the 3G domain to provide abetter and more economical fit.

The steps described herein could be completed or initiated in adifferent order. Steps could be omitted, or one or more steps could beperformed individually, or could be applied only to a subset of bearersor incoming attach requests. For example, special treatment may beapplied only to circuit-switched calls and not to packet data or viceversa.

The method described herein is robust even when encryption is used. Inthe LTE protocol, data is encrypted between the eNodeB and the remoteendpoint. This results in the situation where quality of serviceinformation that is within the encrypted tunnel is not known to theintermediary nodes, causing intermediary nodes to be unable to applyquality of service to the encrypted traffic. For example, signalingtraffic to a management system that is encrypted in the HTTPS protocolmay not be given priority service if it is necessary to look within theencrypted HTTPS data payload. However, the method described herein usesthe RRC establishment cause, which is not encrypted, and the QCI ofpreexisting bearers, which is also not encrypted. Both these QoS flagsare information elements associated with the bearer envelope itself, andthus are available at the eNodeB for inspection.

The above disclosure relates to the network-driven scenario. In someembodiments and use cases, the UE can also perform idle-reselection. Ifthe LTE E-UTRAN is not congested, the re-selection into the LTEtypically could be accepted. But during the congestion scenario, bydefault, re-selection may be rejected, hence re-directing back to the 3Gdomain. We can improve this behavior using the specific UE's historyprofile, tracked for example by IMSI, by which we can predict that thisUE's typical QCI pattern is tied with video traffic etc. In such cases,we could consider deflecting some of the existing E-RABs (QCI=1) intothe 3G network to make room for such LTE re-selection access.

In further embodiments, offload from 3G to LTE is also understood to bepossible using at least the same parameters described above. Forexample, if a UE is capable of LTE as well as 3G, the UE may be steeredto LTE when capacity is not available on 3G. Steering could also bereverted back by the network, for instance, when capacity later becomesavailable.

In some embodiments, handover as well as redirect could be used fornetwork-controlled steering. In some embodiments, proactive steeringcould reduce the likelihood of congestion before congestion occurs. Insome embodiments, non-congestion-related steering could also be used.For example, different RANs may have different backhaul characteristics.Steering according to this disclosure may be used to steer voice callstoward the RAN with better backhaul characteristics for voice calls,such as low latency, while steering noninteractive packet data towardanother RAN. In some embodiments, multiple target RANs may be used forredirection, with the specific target RAN being identified by itsfrequency, in the case that multiple frequencies are available forproviding access.

FIG. 1 is a schematic diagram of a system providing multi-RAT service,according to some embodiments. UE 101 is connected to LTE eNodeB 103.The LTE eNodeB 103 is connected to a coordinating gateway 106, which mayprovide functions such as: self-organizing or self-healing networkproperties; cached or virtualized core network functions; multi-operatorcore network (MOCN) capabilities; eNodeB virtualization; multi-RATcoordination; load coordination with other eNodeBs or other nodeBs; orother functions. In addition, coordinating gateway 106 provides agateway to a serving gateway (SGW) 107 and a packet gateway (PGW) 111and a mobility management entity (MME) 109, which are well-known aspectsof an evolved packet core (EPC) network that provide packet serving,gateway functions to other networks, and mobility management functions.The PGW 111 provides gateway functionality to the public Internet 120.These components constitute a 4G access network and core network.

As well, FIG. 1 shows a 3G nodeB 104, which is connected to a radionetwork controller (RNC) 106, as well as a gateway GPRS support node(GGSN) 108 and serving GPRS support node (SGSN) 110, which constitute a3G (UMTS) access network and core network. The SGSN provides gatewayfunctionality to the Internet 120.

As shown, UE 101 may be redirected from LTE eNodeB 103 to 3G nodeB 104(the post-redirection UE being represented as UE 102). LTE eNodeB 103and 3G nodeB 104 may, in some embodiments, communicate to shareinformation regarding availability, congestion, and load. In someembodiments, load information may be deduced at either eNodeB 103 ornodeB 104 indirectly from measurement reports received by the eNodeB ornodeB from UEs in the area. In some embodiments, base stations 103 and104 may communicate directly via a mesh link, or via Internet 120 andtheir respective core networks.

In some embodiments, LTE eNodeB 103 and 3G nodeB 104 may be located inthe same device, such as in a single multi-RAT base station as shown inFIG. 4. In the case that both base stations are located in the samedevice, the communication between them may be further optimized, forexample by using shared memory, shared file systems, inter-processcommunication, loopback or local network communications, or other means.In some embodiments, 3G core 106, 108, 110 may be emulated bycoordinator 105 such that the LTE core network is leveraged to provideall necessary support for the UE, while the UE is still enabled toconnect to a 3G RAN via nodeB 104.

FIG. 2 is a state diagram showing multiple states of an HSPA and an LTEprotocol stack at a HSPA base station and an LTE base station, inaccordance with some embodiments. High speed packet access (HSPA, e.g.,3G) protocol UE connection states 201 include idle 202 and connected303. The HSPA connected state 203 has several sub-states, namely, 203 a(URA_PCH), 203 b (CELL_PCH), 203 c (CELL_FACH), and 203 d (CELL_DCH).LTE protocol UE connection states 204 include idle 205 and connected206. The connection redirection, reselection, and handover proceduresdescribed elsewhere herein are shown here. Reselection is shown as anidle mode procedure in which either a UE in an LTE IDLE state 205 can becaused to reselect to an HSPA IDLE state 202, or vice versa. Similarly,handover is shown to be a connected mode procedure. A UE that isconnected to an HSPA cell and in state 203 d (CELL_DCH) can be caused tohand over to an LTE cell, entering LTE connected state 206, and viceversa.

Regarding redirection, the state diagram shows that URA_PCH 203 a andCELL_PCH 203 b and CELL_FACH 203 c can be redirected to LTE IDLE 205. Incertain cases, CELL_DCH 203 d can also be redirected to LTE IDLE 205.Circuit-switched fallback (CSFB) involves a redirection from the LTEconnected state 206 to the HSPA idle state 202. Some of the redirectionmethods described herein, such as release of existing LTE bearers at theloaded eNodeB, or redirections involving RRC connection release, mayalso be redirections from the LTE connected state 206 to the HSPA idlestate 202.

In some cases, the network can trigger handover instead of the UE. Thesemechanisms are shown in the below figure in reference to the availableradio resource control (RRC) states for 3G and 4G, and are usedbeneficially by the methods described below.

FIG. 3 is a flowchart showing a method for providing congestion reliefat an eNodeB, in accordance with some embodiments. At step 301,congestion is detected at an eNodeB. This may be detected at the eNodeBitself, or detected at another node, such as a gateway node orcoordination server. Congestion may include one or more of: processorload; baseband load; resource load, resources including radio resourceblocks; bandwidth or backhaul limitations; or other types of load.Congestion may be detected via various means. In some embodiments,measurement reports from UEs may be used. In some embodiments,measurement reports from UEs that are received by neighboring basestations may be used to identify load at a particular base station.

Once congestion has been detected, the methods described herein can beused to offload both new and existing connections so as to reducecongestion at the eNodeB. At step 302, the base station may beginmanaging its congestion by selectively admitting only certainconnections. These connections may be filtered based on the radioresource control (RRC) establishment cause, which is a parametertransmitted by the UE to the base station in making its initialconnection request. Upon entering the RRC connection stage for a new UE,the base station may identify and take into account the RRCestablishment cause of that connection request as a factor indetermining whether to accept the connection request.

At step 303, certain connection requests with certain establishmentcauses may be given preferred treatment by the base station. Forexample, emergency calls and/or emergency requests may be permitted toconnect. As another example, high priority access, such as requests fromoperations and management nodes, may be granted access to connect.However, in the example shown, it may not be possible to accept a newconnection given the loaded state of the base station. Therefore,redirection of existing LTE bearers to 3G may be performed.

LTE bearers to be redirected to 3G may be identified using bearer QCIinformation. Inter-RAT handover or redirection may be required of thosebearers to a 3G cell, such as at a co-located 3G cell within the samebase station of a multi-RAT base station as shown in FIG. 4.

In some embodiments, redirection of existing LTE bearers to 3G accordingto these methods may be performed even without new connection requestsbeing received. For example, once load exceeds a threshold, the basestation may perform redirection of existing LTE bearers to 3G to reduceload until it is again below the threshold.

Step 304 covers the case where an incoming attach request does notinclude an emergency or high priority access RRC establishment request.In such a case, the incoming request may be refused and insteadredirected, using an RRC connection release. Step 305 makes clear that acircuit-switched request may be caused to fall back to acircuit-switched 3G context, and a packet-switched request may be causedto fall back to a packet-switched 3G PDP context.

In some cases, handovers may be required instead of redirections, suchas when a CONNECTED-state circuit-switched context is required to bemoved between RATs.

FIG. 4 is a schematic diagram of an enhanced eNodeB, in accordance withsome embodiments. Enhanced eNodeB 400 may include processor 402,processor memory 404 in communication with the processor, basebandprocessor 406, and baseband processor memory 408 in communication withthe baseband processor. Enhanced eNodeB 400 may also include first radiotransceiver 410 and second radio transceiver 412, internal universalserial bus (USB) port 416, and subscriber information module card (SIMcard) 418 coupled to USB port 414. In some embodiments, the second radiotransceiver 412 itself may be coupled to USB port 416, andcommunications from the baseband processor may be passed through USBport 416.

A multi-RAT coordination module 430 may also be included, and mayperform load monitoring of more than one RAT, including resourcemonitoring for both 3G and 4G RATs. The coordination module 430 maydetermine when to enter a congestion mode as described elsewhere herein,and may perform processing to determine which bearers or contexts shouldbe redirected or reselected or handed over. The multi-RAT coordinationmodule 430 may be in communication with a local evolved packet core(EPC) module 420, for authenticating users, storing and caching priorityprofile information, and performing other EPC-dependent functions whenno backhaul link is available. Local EPC 420 may include local HSS 422,local MME 424, local SGW 426, and local PGW 428, as well as othermodules. Local EPC 420 may incorporate these modules as softwaremodules, processes, or containers. Local EPC 420 may alternativelyincorporate these modules as a small number of monolithic softwareprocesses. Coordination module 430 and local EPC 420 may each run onprocessor 402 or on another processor, or may be located within anotherdevice.

Processor 402 and baseband processor 406 are in communication with oneanother. Processor 402 may perform routing functions, and may determineif/when a switch in network configuration is needed. Baseband processor406 may generate and receive radio signals for both radio transceivers410 and 412, based on instructions from processor 402. In someembodiments, processors 402 and 406 may be on the same physical logicboard. In other embodiments, they may be on separate logic boards.

The first radio transceiver 410 may be a radio transceiver capable ofproviding LTE eNodeB functionality, and may be capable of higher powerand multi-channel OFDMA. The second radio transceiver 412 may be a radiotransceiver capable of providing LTE UE functionality. Both transceivers410 and 412 are capable of receiving and transmitting on one or more LTEbands. In some embodiments, either or both of transceivers 410 and 412may be capable of providing both LTE eNodeB and LTE UE functionality.Transceiver 410 may be coupled to processor 402 via a PeripheralComponent Interconnect-Express (PCI-E) bus, and/or via a daughtercard.As transceiver 412 is for providing LTE UE functionality, in effectemulating a user equipment, it may be connected via the same ordifferent PCI-E bus, or by a USB bus, and may also be coupled to SIMcard 418.

SIM card 418 may provide information required for authenticating thesimulated UE to the evolved packet core (EPC). When no access to anoperator EPC is available, local EPC 420 may be used, or another localEPC on the network may be used. This information may be stored withinthe SIM card, and may include one or more of an international mobileequipment identity (IMEI), international mobile subscriber identity(IMSI), or other parameter needed to identify a UE. Special parametersmay also be stored in the SIM card or provided by the processor duringprocessing to identify to a target eNodeB that device 400 is not anordinary UE but instead is a special UE for providing backhaul to device400.

Wired backhaul or wireless backhaul may be used, including mesh backhaulbetween mesh base stations or mesh relay nodes. Wired backhaul may be anEthernet-based backhaul (including Gigabit Ethernet), or a fiber-opticbackhaul connection, or a cable-based backhaul connection, in someembodiments. Additionally, wireless backhaul may be provided in additionto wireless transceivers 410 and 412, which may be Wi-Fi802.11a/b/g/n/ac/ad/ah, Bluetooth, ZigBee, microwave (includingline-of-sight microwave), or another wireless backhaul connection. Anyof the wired and wireless connections may be used for either access orbackhaul, according to identified network conditions and needs, and maybe under the control of processor 402 for reconfiguration.

Other elements and/or modules may also be included, such as a homeeNodeB, a local gateway (LGW), a self-organizing network (SON) module,or another module. Additional radio amplifiers, radio transceiversand/or wired network connections may also be included.

Processor 402 may identify the appropriate network configuration, andmay perform routing of packets from one network interface to anotheraccordingly. Processor 402 may use memory 404, in particular to store arouting table to be used for routing packets. Baseband processor 406 mayperform operations to generate the radio frequency signals fortransmission or retransmission by both transceivers 410 and 412.Baseband processor 406 may also perform operations to decode signalsreceived by transceivers 410 and 412. Baseband processor 406 may usememory 408 to perform these tasks.

In some embodiments, the enhanced eNodeB 400 may include both 3G and LTEfunctionality, including nodeB and eNodeB functionality. The combinationof both 3G and LTE functionality in the same base station allows forsynergies in relation to the present application. For example, in someembodiments, shared memory, inter-process communication, or an internalnetwork switch may be used to share load information between the 3G and4G base stations. This may result in the 3G base station being able toinform the 4G base station that it is not heavily loaded and has voicebearer capacity to spare, or for the LTE base station to communicate ina lightweight way to the 3G base station that it is loaded withoutrequiring specialized protocols for communicating, for example.

FIG. 5 is a schematic diagram of a gateway, in accordance with someembodiments. Coordination server 500 includes processor 502 and memory504, which are configured to provide the functions described herein.Also present are radio access network coordination/signaling (RANCoordination and signaling) module 506, RAN proxying module 508, androuting virtualization module 510. In some embodiments, coordinationserver 500 may coordinate multiple RANs using coordination module 506.In some embodiments, coordination server may also provide proxying,routing virtualization and RAN virtualization, via modules 510 and 508.In some embodiments, a downstream network interface 512 is provided forinterfacing with the RANs, which may be a radio interface (e.g., LTE),and an upstream network interface 514 is provided for interfacing withthe core network, which may be either a radio interface (e.g., LTE) or awired interface (e.g., Ethernet). Inter-RAT coordination functions suchas those described herein may be coordinated or performed in module 506.For example, information about load from other base stations in thenetwork may be forwarded to other nodes, thereby facilitating themethods described herein.

Coordination server 500 includes local evolved packet core (EPC) module520, for authenticating users, storing and caching priority profileinformation, and performing other EPC-dependent functions when nobackhaul link is available. Local EPC 520 may include local HSS 522,local MME 524, local SGW 526, and local PGW 528, as well as othermodules. Local EPC 520 may incorporate these modules as softwaremodules, processes, or containers. Local EPC 520 may alternativelyincorporate these modules as a small number of monolithic softwareprocesses. Modules 506, 508, 510 and local EPC 520 may each run onprocessor 502 or on another processor, or may be located within anotherdevice.

In some embodiments, the radio transceivers described herein may be basestations compatible with a Long Term Evolution (LTE) radio transmissionprotocol or air interface. The LTE-compatible base stations may beeNodeBs. In the foregoing disclosure, the term 3G is used to refer toUMTS, HSPA, HSPA+, or CDMA/CDMA2000, as appropriate, and the term 4G isused interchangeably with LTE. In addition to supporting the LTEprotocol, the base stations may also support other air interfaces, suchas UMTS/HSPA, CDMA/CDMA2000, GSM/EDGE, GPRS, EVDO, other 3G/2G, legacyTDD, or other air interfaces used for mobile telephony. In someembodiments, the base stations described herein may support Wi-Fi airinterfaces, which may include one or more of IEEE 802.11a/b/g/n/ac. Insome embodiments, the base stations described herein may support IEEE802.16 (WiMAX), to LTE transmissions in unlicensed frequency bands(e.g., LTE-U, Licensed Access or LA-LTE), to LTE transmissions usingdynamic spectrum access (DSA), to radio transceivers for ZigBee,Bluetooth, or other radio frequency protocols, or other air interfaces.In some embodiments, the base stations described herein may useprogrammable frequency filters. In some embodiments, the base stationsdescribed herein may provide access to land mobile radio(LMR)-associated radio frequency bands. In some embodiments, the basestations described herein may also support more than one of the aboveradio frequency protocols, and may also support transmit poweradjustments for some or all of the radio frequency protocols supported.The embodiments disclosed herein can be used with a variety of protocolsso long as there are contiguous frequency bands/channels. Although themethod described assumes a single-in, single-output (SISO) system, thetechniques described can also be extended to multiple-in, multiple-out(MIMO) systems. Wherever IMSI or IMEI are mentioned, other hardware,software, user or group identifiers, can be used in conjunction with thetechniques described herein.

The foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. In some embodiments, softwarethat, when executed, causes a device to perform the methods describedherein may be stored on a computer-readable medium such as a computermemory storage device, a hard disk, a flash drive, an optical disc, orthe like. As will be understood by those skilled in the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. For example, wirelessnetwork topology can also apply to wired networks, optical networks, andthe like. The methods may apply to LTE-compatible networks, toUMTS-compatible networks, to Wi-Fi networks, networks in an unlicensedband, including 3GPP networks (LTE-U/LTE-AA), or to networks foradditional protocols that utilize radio frequency data transmission.Various components in the devices described herein may be added,removed, or substituted with those having the same or similarfunctionality. Various steps as described in the figures andspecification may be added or removed from the processes describedherein, and the steps described may be performed in an alternativeorder, consistent with the spirit of the invention. Features of oneembodiment may be used in another embodiment. Accordingly, thedisclosure of the present invention is intended to be illustrative of,but not limiting of, the scope of the invention, which is specified inthe following claims.

The invention claimed is:
 1. A method, comprising: detecting congestionat an eNodeB and entering a congestion control mode; receiving, at theeNodeB, a new user equipment (UE) connection request that contains aradio resource control (RRC) establishment cause; determining, at theeNodeB, a priority of the new UE connection request based on the RRCestablishment cause, wherein the priority of the new UE connectionrequest is based on a RRC establishment cause in the new UE connectionrequest; and identifying, at the eNodeB, the congestion managementstrategy based on the priority of the new UE connection request, thecongestion management strategy comprising both of initiating a handoverfor an existing LTE bearer and redirecting the new UE connection requestto a multi-radio access technology (multi-RAT) eNodeB, the multi-RATeNodeB having LTE and 3G radio capability.
 2. The method of claim 1,wherein detecting congestion at the eNodeB is performed at the eNodeB.3. The method of claim 1, wherein detecting congestion at the eNodeB isperformed at a coordinating server.
 4. The method of claim 1, whereinthe eNodeB is a multi-radio access technology (multi-RAT) eNodeB with anintegrated UMTS nodeB.
 5. The method of claim 1, further comprisingusing a quality of service class identifier (QCI) of the existing LTEbearer to determine whether to evacuate the existing LTE bearer.
 6. Themethod of claim 1, wherein the congestion management strategy comprisesinitiating a handover for an existing LTE bearer if the new UEconnection request has an RRC establishment cause of either emergency orhigh priority access.
 7. The method of claim 1, further comprisingredirecting the new UE connection request that is a request for apacket-switched (PS) data connection to a multi-RAT eNodeB.
 8. Themethod of claim 1, further comprising redirecting a mobile originatingdata connection request to a multi-RAT eNodeB.
 9. The method of claim 1,further comprising identifying a plurality of LTE bearers to be handedover from lowest to highest QCI value.
 10. The method of claim 1,further comprising exiting the congestion control mode once congestionat the eNodeB is resolved.
 11. The method of claim 1, further comprisingredirecting multi-RAT connections back to the LTE eNodeB once congestionat the eNodeB is resolved.
 12. The method of claim 1, further comprisingdetecting congestion by tracking one or more of: processor load;physical resource block (PRB) usage; physical downlink control channelcontrol channel elements (PDCCH CCEs); number of total user equipmentsserved; and backhaul bandwidth utilization.
 13. A non-transitory digitalstorage medium comprising instructions that, when executed by a basestation, causes the computer to perform steps comprising: detectingcongestion at an eNodeB and entering a congestion control mode;receiving, at the eNodeB, a new user equipment (UE) connection requestthat contains a radio resource control (RRC) establishment cause;determining, at the eNodeB, a priority of the new UE connection requestbased on the RRC establishment cause, wherein the priority of the new UEconnection request is based on a RRC establishment cause in the new UEconnection request; and identifying, at the eNodeB, the congestionmanagement strategy based on the priority of the new UE connectionrequest, the congestion management strategy comprising both ofinitiating a handover for an existing LTE bearer and redirecting the newUE connection request to a multi-radio access technology (multi-RAT)eNodeB, the multi-RAT eNodeB having LTE and 3G radio capability.
 14. Themethod of claim 1 wherein the RRC establishment cause is one ofemergency; high priority access; mobile terminating access; mobileoriginating signaling; and mobile originating data.
 15. Thenon-transitory digital storage medium of claim 13 wherein the RRCestablishment cause is one of emergency; high priority access; mobileterminating access; mobile originating signaling; and mobile originatingdata.